Truxene-based columnar liquid crystals: Self-assembled structures and electro-active properties

Article abstract of DOI:10.1002/asia.200900038

Columnar liquid-crystalline (LC) truxene derivatives containing branched flexible alkyl chains have been designed and synthesized. The dicyanomethylene and dithiafulvene substituents have been introduced into the π-conjugated truxene framework to tune the

Full text of DOI:10.1002/asia.200900038

DOI: 10.1002/asia.200900038
Truxene-Based Columnar Liquid Crystals: Self-Assembled Structures and
Electro-Active Properties
Kyosuke Isoda, Takuma Yasuda, and Takashi Kato*[a]
Abstract: Columnar liquid-crystalline
(LC) truxene derivatives containing
branched flexible alkyl chains have
been designed and synthesized. The di-
cyanomethylene and dithiafulvene sub-
stituents have been introduced into the
p-conjugated truxene framework to
tune their electronic and redox proper-
ties as well as the molecular assembled
structures. The p-conjugated cores of
dicyanomethylene- and dithiafulvene-
appended truxenes adopt bowl-shaped
conformations, giving rise to a large in-
trinsic dipole moment perpendicular to
the aromatic framework. These mole-
cules form stable columnar LC struc-
tures through intermolecular dipole–
dipole interactions. The redox proper-
ties of LC truxene derivatives have
been examined by cyclic voltammetry.
The dicyanomethylene-appended trux-
ene shows the reversible four-step elec-
trochemical reductions, whereas the di-
thiafulvene-appended truxene under-
goes three-step oxidations.
Keywords: cyclic voltammetry
·
liquid crystals · redox chemistry ·
self-assembly · semiconductors
Introduction
tures and exhibit redox-active behavior.[13] In the present
study, we have focused on C3-symmetrical truxene-based
molecules having larger p-conjugated structures as the
redox- and electro-active cores of the columnar LC materi-
als.
Truxenes have been studied as potential materials for the
molecular fragments of fullerene,[14] electronic materials,[15]
and liquid crystals.[16] Our intention is to tune the electronic
properties of truxene-based liquid crystals by the introduc-
tion of electron-accepting dicyanomethylene or electron-do-
nating dithiafulvene moieties into the p-conjugated core.
The substitution can also affect the molecular structures of
the truxene framework, resulting in the formation of bowl-
shaped cores.
Supramolecular self-organization of p-conjugated molecules
into ordered nanostructures is crucial for the development
of electro-functional soft materials in future molecular-
based devices.[1] Columnar liquid crystals[2,3] are a class of
dynamically functional soft materials that can allow trans-
portation of charges[4] and ions,[5] gas and molecular separa-
tion,[6] and photonics applications.[7] Discotic molecules such
as triphenylenes,[4a,b] hexabenzocoronenes,[1a,h,4c,d] and phtha-
locyanines[4e,f] possessing planar p-conjugated structures
have been well-established as columnar liquid crystals, and
they can be used as charge-transporting materials.[4]
Recently, liquid-crystalline (LC) molecules with uncon-
ventional shapes have received much attention as a new
class of functional columnar materials.[3] For example, fan-
shaped,[5a,b,8] cone-shaped,[9] macrocyclic,[10] dendritic,[11] pol-
ycatenar mesogens[12] have been developed. We have report-
ed that roof-shaped p-conjugated tetracyanoanthraquinodi-
methane derivatives self-assemble into columnar LC struc-
Herein, we report redox and photoconductive properties
of truxene-based liquid crystals 1–3 (Scheme 1). These
modified truxene derivatives are expected to function as n-
and p-type semiconducting LC materials.
Results and Discussion
[a] K. Isoda, Dr. T. Yasuda, Prof. T. Kato
Department of Chemistry and Biotechnology
School of Engineering
Synthesis of Truxene Derivatives
We have synthesized truxene derivatives 1–3 as outlined in
Scheme 1 (see Experimental and Supporting Information
for details). To induce mesomorphic properties, the
branched flexible alkyl chains are attached to the rigid fused
aromatic cores. Truxenone 3 has been obtained by Suzuki-
coupling reaction[17] of 4,9,14-tribromotruxenone 4[18] with
The University of Tokyo
Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)
Fax : (+81)3-5841-8661
E-mail: kato@chiral.t.u-tokyo.ac.jp
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.200900038.
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Scheme 1. Synthesis of truxene derivatives 1–3. Reagents and conditions: (i) 5, PdACTHNUTRGNEG(UN PPh3)4, K2CO3, THF/H2O, 60 8C, 24 h; (ii) 6, DABCO, TiCl4, pyridine,
CH2Cl2, room temperature, 0.5 h; (iii) 7, nBuLi, THF, À788C to room temperature, overnight.
three equivalents of boronate 5 in the presence of Pd-
(PPh3)4 as the catalyst. Dicyanomethylene-appended trux-
ene 1 has been synthesized by Knoevenagel condensation of
3 with Lehnertꢁs reagent,[20] which is prepared from malono-
nitrile 6, TiCl4, and pyridine. Dithiafulvene-appended trux-
ene 2 has been prepared by Horner–Emmons reaction[21] be-
tween 3 and phosphonate 7[22] in the presence of butyllithi-
[19]
um.[23] The chemical structures of compounds 1–3 are ascer-
1
tained by H and 13C NMR, IR spectroscopy, matrix-assisted
laser desorption ionization time-of-flight (MALDI-TOF)
mass spectrometry, and elemental analysis. The IR spectrum
ꢀ
of 1 exhibits the characteristic C N stretching band at
2222 cmÀ1, instead of the C=O stretching band at 1706 cmÀ1
observed for 3. Furthermore, the lowest energy absorption
maxima of 1 and 2 are observed at 404 and 458 nm, respec-
tively, which exhibit significant bathochromic shift from that
of 3 (336 nm) arising from the expansion of the p-conjugat-
ed structures (Figure 1).
Abstract in Japanese:
Liquid-Crystalline Properties and Structures
The LC properties of truxene derivatives 1–3 are summar-
ized in Table 1. The set of the compounds exhibits columnar
LC phases over wide temperature ranges including room
temperature. DSC thermograms of 2 (Figure 2) show only a
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Truxene-Based Columnar Liquid Crystals
Figure 1. UV/Vis absorption spectra of 1 (solid line), 2 (dashed line), and
3 (dotted line) in CH2Cl2.
Table 1. Liquid-crystalline properties of 1–3.
Figure 3. Polarized optical photomicrographs of a) 1 and b) 2 in the Col
phases, and c) 3 in the Colh phase at 258C. d) Dendritic growth of a Colh
domain of 3 upon cooling from the isotropic state with uncrossed polariz-
ers.
Compound
Phase transition behavior[a]
1
2
3
[b] Col 245 (17) Iso
[b] Col 161 (24) Iso
[b] Colh 106 (2) Iso
[a] Transition temperatures (8C) and enthalpy changes (kJmolÀ1, in pa-
rentheses) determined by DSC on second heating at 58C minÀ1. Col: col-
umnar; Colh: hexagonal columnar; Iso: isotropic. [b] No distinct transi-
tion peaks are detected on DSC above À508C.
originate from variations in the conformation and polarity
of their fused aromatic cores. Unlike the planar structure of
truxenone 3, the fused aromatic cores of 1 and 2 adopt
highly distorted bowl-shaped conformations as displayed in
Figure 4, because of steric repulsions between three dicyano-
Figure 2. DSC thermograms of 2 at 58CminÀ1. Col: columnar; Iso: iso-
tropic; Ti: isotropization temperature.
clear transition peak at 1408C from the isotropic to the col-
umnar LC phase on cooling. For compounds 1 and 2, bire-
fringent leaf-like and fan-like textures are observed using a
polarized optical microscope (Figure 3a,b), which are char-
acteristic of columnar liquid crystals.[24] The X-ray diffrac-
tion (XRD) patterns of 1 and 2 observed at 258C show an
intense reflection peak at 25.9 and 27.5 ꢂ, respectively, in
the small-angle region (see Supporting Information). While
distinct higher-order reflections could not be detected in the
XRD patterns of 1 and 2, the polarized optical microscopic
observations suggest the formation of the columnar (Col)
LC phases. Compound 3 exhibits a dendritic growth of an
LC domain typical of the hexagonal columnar (Colh) LC
phase upon cooling from the isotropic state (Figure 3c,d).
It should be pointed out that the isotropization tempera-
tures and the corresponding transition enthalpies for 1 and 2
are much higher than those observed for 3 (Table 1) despite
the same peripheral substituents. This difference should
Figure 4. Optimized geometries of the fused aromatic cores for a) 1, b) 2,
and c) 3 calculated at the B3LYP/6-31G* level: top view (left) and side
view (right). Atoms color code: H white, C gray, N blue, O red, S yellow.
Arrows indicate the dipole moment.
methylene or dithiafulvene substituents and the adjacent hy-
drogen atoms.[20c,23] It has also been revealed that the bowl-
shaped aromatic cores of 1 and 2 possess a large intrinsic
dipole moment of 10.1 and 3.8 debye, respectively, along the
C3 axis (Figure 4). Accordingly, as for these highly polar
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T. Kato et al.
FULL PAPERS
mesogenic molecules, strong longitudinal dipole–dipole in-
termolecular interactions should be the driving force for the
formation and stabilization of columnar molecular assem-
blies.[13] Moreover, nanosegregation of the polar aromatic
cores of 1 and 2 from surrounding alkyl moieties can facili-
tate the stabilization of the columnar structures. The bowl-
shaped molecules of 1 and 2 should stack with one another
in a head-to-tail manner within each column (Figure 5), and
cal properties of 1–3 have been tuned by the substituents in-
troduced into the p-conjugated truxene cores. The cyclic
voltammogram of 1 having three electron-withdrawing di-
cyanomethylene substituents exhibits reversible four-step re-
duction waves at the half-wave potentials (E1/2) of À0.80,
À1.14, À1.43, and À2.02 V versus Fc+/Fc. These redox
waves are ascribed to the formation of tetraanionic species.
The successive three one-electron reduction steps in such a
narrow potential range would be centered on three different
dicyanomethylene units. Therefore, each redox-active unit
should be coupled with respect to one another through the
p-conjugated truxene scaffold.
It is noteworthy that the multistep redox behavior of 1 is
comparable with the results for C60 fullerene reported by
Echegoyen and co-workers.[27] Furthermore, the first reduc-
tion of 1 (E1/2 =À0.80 V vs Fc+/Fc) occurs at a less negative
potential than those of C60 fullerene (E1/2 =À0.96 V) as well
as homologous truxenone 3 (E1/2 =À1.42 V), indicative of
the extremely high electron-accepting capability of 1. In
contrast to 1 and 3, compound 2 with three electron-donat-
ing dithiafulvene units undergoes reversible three-step oxi-
dations in a positive potential region, originating from the
formation of a radical trication by electrochemical oxida-
tions on three dithiafulvene units.
The HOMO (highest occupied molecular orbital) and the
LUMO (lowest unoccupied molecular orbital) energy levels
(EHOMO and ELUMO) of truxene derivatives 1–3 can be evalu-
ated from the cyclic voltammetry and UV/Vis spectroscopic
data,[28] as shown in Figure 7 and Table 2. It has been re-
Figure 5. Representation of a possible self-assembled columnar structure
involving eight stacked molecules of 1.
the columns could be arranged in an antiparallel manner to
cancel the macroscopic dipole repulsion between the col-
umns. Such polar columnar assemblies were proposed for
columnar liquid crystals incorporating C60 fullerene,[9c–e] tri-
phenylphosphine oxide,[9a] and urea moiety[25] as the cores.
Redox Behavior
The redox-active LC materials have attractive attention for
the development of new functional soft materials.[9e,11c,12f,13,26]
The redox behavior of truxene derivatives 1–3 has been
studied by cyclic voltammetry (Figure 6). The electrochemi-
Figure 7. Comparison of the HOMO and LUMO energy levels for trux-
ene derivatives 1–3.
vealed that the electronic properties of these compounds
are strongly dependent on the substituents attached to the
truxene core. The significant stabilization of ELUMO in 1
(À4.08 eV) compared to that in truxenone 3 (À3.40 eV) is
attributed to the strong electron-withdrawing effect of the
dicyanomethylene substituents. In contrast, EHOMO of dithia-
fulvene-appended 2 (À4.96 eV) is much higher than those of
1 and 3, implying a high electron-donating ability of 2.
Therefore, compounds 1 and 2 are expected to function as
electron- and hole-transporting materials, respectively.
Figure 6. Cyclic voltammograms of a) 1, b) 2, and c) 3 (2.0 mm) recorded
in CH2Cl2 solution of [(C4H9)4N]ClO4 (0.10m).
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Truxene-Based Columnar Liquid Crystals
Table 2. Spectroscopic and electrochemical data of 1–3.
Compound
UV/Vis absorption
lmax [nm]
Redox potential (V vs Fc+/Fc)[a]
ELUMO[b] [eV]
EHOMO[c] [eV]
Egopt[d] [eV]
1
2
3
4
E1/2
E1/2
E1/2
E1/2
1
2
3
283, 404
309, 432, 458
336
À0.80
0.22
À1.42
À1.14
0.43
À1.83
À1.43
0.64
–
À2.02
À4.08
À2.72
À3.40
À6.13
À4.96
À5.96
2.05
2.24
2.56
–
–
[a] Measured by cyclic voltammetry in CH2Cl2 solution of [(C4H9)4N]ClO4 (0.10m). [b] For 1 and 3, ELUMO is calculated from the onset reduction potential
with the assumption that the energy level of ferrocene is 4.8 eV below vacuum level[28]: ELUMO =ÀEonset(red)À4.8 eV. For 2, ELUMO is calculated by the
equation: ELUMO =EHOMO+Egopt. [c] For 1 and 3, EHOMO is calculated by the equation: EHOMO =ELUMOÀEgopt. For 2, EHOMO is calculated from the onset ox-
idation potential: EHOMO =ÀEonset(ox)À4.8 eV. [d] Estimated from the onset position of the UV/Vis absorption spectrum in CH2Cl2: Egopt =1240/lonset
.
give electron mobilities of 3ꢃ10À4 and 5ꢃ10À4 cm2 VÀ1 sÀ1,
respectively, in the Col phases at 1008C (Supporting Infor-
mation). There are only a few reports of electron-mobility
measurements in Col phases.[30] The carrier mobilities of
compounds 1 and 2 with the bowl-shaped cores are compa-
rable to those of 3 as well as to the triphenylenes[4a] in spite
of the distorted nonplanar p-conjugated structures. These
results indicate that the columnar stacks comprised of dis-
torted bowl-shaped p-conjugated cores are capable of trans-
porting charge carriers along the columns.
Photoconductivity
The carrier transport properties of the truxene derivatives in
the Col phases have been examined using the time-of-flight
(TOF) method.[29] The hole and electron mobilities can be
detected individually by switching the polarity of the applied
electric fields. Compounds 1 and 3 show electron-transport-
ing (n-type) characteristics, whereas hole transport can be
observed for 2. Figure 8a shows typical transient photocur-
Conclusions
We have prepared C3-symmetrical truxene derivatives 1–3
that exhibit columnar LC phases over wide temperature
ranges. Compounds 1 and 2, containing bowl-shaped cores,
self-assemble into stable columnar LC nanostructures by
means of intermolecular dipole–dipole interactions as well
as nanosegregation between the polar aromatic cores and
the nonpolar alkyl moieties. The redox and electronic prop-
erties of the truxene derivatives can be tuned by the sub-
stituents incorporated into the p-conjugated truxene core.
Dicyanomethylene- and dithiafulvene-appended truxenes 1
and 2 show reversible multivalent redox behavior in a
narrow potential range. These LC molecules serve as n- and
p-type semiconducting materials, and exhibit the carrier mo-
bilities on the order of 10À4 cm2 VÀ1 sÀ1. p-Conjugated trux-
ene-based liquid crystals would be a candidate as electro-
active materials for the fabrication of photovoltaic cells and
molecular batteries.
Figure 8. a) Transient photocurrent curves for holes of 2 in the Col phase
at 1008C and b) temperature dependence of hole mobility for 2 in the
Col phase at 1.25ꢃ105 VcmÀ1 upon cooling.
Experimental Section
General Methods
rent curves for holes of 2 at 1008C under the applied electric
fields. The photocurrents for holes exhibit a plateau, and the
transit time of the photogenerated charge carriers gets
longer upon reducing the applied electric field. From these
data, the hole mobility of 2 is calculated to be 5ꢃ
10À4 cm2 VÀ1 sÀ1. The hole mobilities of 2 in the Col phase
are almost constant in the temperature range of 60–1208C
(Figure 8b), which is similar to carrier-transport behavior in
conventional discotic liquid crystals.[4a] In contrast, com-
pounds 1 and 3 exhibit electron-transporting properties and
1H and 13C NMR spectra were recorded on a JEOL JNM-LA400 spec-
1
trometer. Chemical shifts of H and 13C NMR signals were quoted to tet-
ramethylsilane (d=0.00) and CDCl3 (d=77.0) as internal standards, re-
spectively. MALDI-TOF mass spectra were collected on a PerSeptive
Biosystems Voyager-DE STR spectrometer using dithranol as the matrix.
Elemental analyses were carried out with a Yanaco MT-6 CHN autocor-
der. DSC measurements were performed on a NETZSCH DSC204 Phoe-
nix calorimeter at a scanning rate of 58CminÀ1. The phase transition tem-
peratures were taken at the onset position of transition peaks in the DSC
traces. An Olympus BH-51 polarizing optical microscope equipped with
a Mettler FP90/82 HT hot stage was used for visual observation of optical
textures. XRD patterns were obtained using a Rigaku RINT-2500 diffrac-
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1623

T. Kato et al.
FULL PAPERS
tometer with a heating stage using Ni-filtered CuKa radiation. UV/Vis ab-
sorption spectra were measured with a JASCO V-670 spectrometer. IR
spectra were recorded on a JASCO FT/IR-660 Plus spectrometer. Cyclic
voltammetry (CV) was carried out in CH2Cl2 solution of [(C4H9)4N]ClO4
(0.10m) with Pt working and counter electrodes, and an Ag+/Ag refer-
ence electrode using an ALS CHI 600B electrochemical analyzer. All po-
tentials were calibrated with Fc+/Fc couple using ferrocene as an internal
reference. The density functional theory (DFT) calculations were carried
out using Wavefunction SPARTAN’04 (ver. 1.0.3) programs. The ground-
state geometries were optimized at the B3LYP/6-31G* level of theory.[31]
Molecular mechanics calculations were performed with the COMPASS
force-field using Accelrys MS Modeling (ver. 4.0) software.
(4.72), 458 nm (4.77); IR (KBr): n˜ =2925, 2856, 1594, 1505, 1453, 1218,
1163, 1054, 814, 645 cmÀ1 1H NMR (400 MHz, CDCl3): d=7.87 (d, J=
;
8.0 Hz, 3H), 7.69 (dd, J=8.0, 0.8 Hz, 3H), 7.46 (d, J=0.8 Hz, 3H), 6.83
(d, J=1.6 Hz, 6H), 6.79 (d, J=6.8 Hz, 3H), 6.71 (d, J=6.8 Hz, 3H), 6.44
(t, J=1.6 Hz, 3H), 3.87 (d, J=5.2 Hz, 12H), 1.85–1.80 (m, 6H), 1.50–1.10
(m, 144H), 0.90–0.85 ppm (m, 36H); 13C NMR (100 MHz, CDCl3): d=
160.76, 143.43, 140.17, 138.63, 136.92, 136.65, 135.13, 128.88, 125.38,
124.30, 123.17, 121.83, 120.97, 118.11, 105.38, 100.37, 70.58, 38.17, 31.92,
31.47, 30.29, 30.10, 29.77, 29.66, 29.38, 26.96, 26.94, 22.72, 22.69,
14.14 ppm; MS (MALDI): m/z calcd: 2312.55 [M+H]+; found: 2312.51;
elemental analysis: calcd (%) for C150H222O6S6: C 77.86, H 9.67; found:
C 77.58, H 9.75.
4,9,14-Tris
4 (0.31 g, 0.50 mmol) and 5 (1.16 g, 1.70 mmol) in dry THF (30 mL) were
added Pd(PPh3)4 (0.06 g, 0.05 mmol) and aqueous K2CO3 (2.0m, 13.0 mL;
ACHTUNGERTN[NUNG 3,5-(2-hexyldecyloxy)phenyl]truxenone (3): To a suspension of
Mobility Measurements
AHCTUNGTRENNUNG
Hole and electron mobilities of the LC materials were evaluated by a
time-of-flight (TOF) technique.[29] The sample was injected into a liquid
crystal cell (cell-gap=4 or 9 mm) consisting of two ITO-coated glass elec-
trodes, by capillary action at an isotropic temperature. No particular
treatment of the electrode surface was made. The sample cell was then
mounted on a hot stage whose temperature was controlled by a thermo-
controller. One side of the sample cell was irradiated by pulse laser
(THG of Nd:YAG; l=355 nm, pulse width=1 ns) under application of
an electric field. The photo-generated charge carriers were pulled across
the sample layer towards the counter electrode. The transient photocur-
rents were monitored using a Tektronix TDS 3044B digital oscilloscope.
The transit time (tT) of charge carriers was determined from the inflec-
tion point of the transient photocurrent curve. The carrier mobility (m)
was calculated using the equation, m=L2/tT·V, in which L is the sample
thickness (4 or 9 mm) and V is the applied voltage. All the TOF measure-
ments were carried out under ambient atmosphere.
Ar bubbled before use). The mixture was vigorously stirred for 24 h at
608C. After cooling to room temperature, the reaction mixture was
poured into water, and extracted with CHCl3 three times. The combined
organic layers were washed with brine, and dried over anhydrous
Na2SO4. After filtration and evaporation, the crude product was purified
by column chromatography (silica, CHCl3/hexane=3:2, v/v), recrystal-
lized from CHCl3/methanol, and dried under vacuum to afford 3 as a
brown waxy solid (0.91 g, 89%). UV/Vis (CH2Cl2): lmax (log e)=336 nm
(4.95); IR (KBr): n˜ =2925, 2856, 1706, 1597, 1456, 1334, 1164, 1057, 829,
803, 674 cmÀ1 1H NMR (400 MHz, CDCl3): d=9.57 (s, 3H), 7.75 (d, J=
;
8.0 Hz, 3H), 7.66 (d, J=8.0 Hz, 3H), 6.94 (d, J=2.0 Hz, 6H), 6.57 (t, J=
2.0 Hz, 3H), 3.97 (d, J=5.2 Hz, 12H), 1.85–1.80 (m, 6H), 1.50–1.10 (m,
144H), 0.87–0.84 ppm (m, 36H); 13C NMR (100 MHz, CDCl3): d=
191.27, 161.03, 148.75, 147.30, 142.10, 142.06, 134.86, 130.61, 130.32,
127.50, 124.09, 106.13, 101.62, 71.23, 38.03, 31.92, 31.90, 31.38, 30.11,
29.77, 29.65, 29.39, 26.89, 26.86, 22.71, 22.68, 14.12 ppm; MS (MALDI):
m/z calcd: 2054.65 [M+H]+; found: 2054.82; elemental analysis: calcd
(%) for C141H216O9: C 82.40, H 10.59; found: C 82.29, H 10.79.
Syntheses
4,9,14-Tris
truxene (1): To a mixture of 3 (0.43 g, 0.21 mmol), malononitrile 6
(0.42 g, 6.3 mmol), and 1,4-diazabicyclo[2.2.2]octane (DABCO, 1.4 g,
ACHTUNGTRENNUNG[3,5-di(2-hexyldecyloxy)phenyl]-1,6,11-tris(dicyanomethylene)-
AHCTUNGTRENNUNG
12.6 mmol) in dry CH2Cl2 (50 mL) were added slowly TiCl4 (1.4 mL), fol-
lowed by pyridine (1.0 mL) at room temperature. The mixture was al-
lowed to react for 30 min, and then poured into water. The product was
extracted with CHCl3 three times. The combined organic layers were
washed with brine, and dried over anhydrous Na2SO4. After filtration
and evaporation, the crude product was purified by column chromatogra-
phy (silica, CHCl3/hexane=4:1, v/v), recrystallized from CHCl3/metha-
nol, and dried under vacuum to afford 1 as a red waxy solid (0.22 g,
48%). UV/Vis (CH2Cl2): lmax (log e)=283 (4.86), 404 nm (4.97); IR
Acknowledgements
This work was partially supported by Grant-in-Aid for Creative Scientific
Research of “Invention of Conjugated Electronic Structures and Novel
Functions” (No. 16GS0209) (T.K.) from the Japan Society for the Promo-
tion of Science (JSPS) and for the Global COE Program for Chemistry
Innovation (T.K. and K.I.) from the Ministry of Education, Culture,
Sports, Science and Technology. We also thank Prof. Masahiro Funahashi
and Dr. Tatsuya Nishimura for helpful discussion and Ms. Kimiyo Saeki
for elemental analyses at The University of Tokyo. T.Y. is grateful for fi-
nancial support from the JSPS Research Fellowship for Young Scientists.
(KBr): n˜ =2921, 2856, 2222, 1600, 1549, 1456, 1331, 1166, 1056, 822 cmÀ1
;
1H NMR (400 MHz, CDCl3): d=8.48 (d, J=8.0 Hz, 3H), 7.85 (s, 3H),
7.78 (d, J=8.0 Hz, 3H), 6.78 (d, J=1.6 Hz, 6H), 6.59 (t, J=1.6 Hz, 3H),
3.94 (d, J=5.6 Hz, 12H), 1.85–1.80 (m, 6H), 1.50–1.10 (m, 144H), 0.89–
0.85 ppm (m, 36H); 13C NMR (100 MHz, CDCl3): d=162.58, 161.24,
147.22, 144.48, 140.94, 139.11, 135.78, 133.55, 130.96, 126.59, 126.23,
113.88, 112.81, 105.88, 102.13, 78.16, 71.20, 38.03, 31.90, 31.86, 31.38,
31.34, 30.03, 29.69, 29.59, 29.34, 26.87, 26.85, 22.67, 14.12 ppm; MS
(MALDI): m/z calcd: 2198.69 [M+H]+; found: 2198.32; elemental analy-
sis: calcd (%) for C150H216N6O6: C 81.92, H 9.90, N 3.82; found: C 81.73,
H 10.08, N 3.68.
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Received: January 28, 2009
Published online: June 24, 2009
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